As said before... Corolla/JDM Inlet Manifold Either a good panel filter in the standard airbox, or an open filter with a nice supply of cold air (IMO open filter is best, airbox seems restrictive to me) Exhaust manifold, such as an OBX or Pacesetter And a good exhaust system, make sure it's no bigger than 2" diameter and no silly 5" backbox Also make sure the car is running nicely, with good sparkplugs/HT leads/dizzy cap/rotor arm etc... and some fresh oil Advancing the ignition timing could help too but I don't know much about that and want to look into it myself. Most people will stop after rolla mani/airfilter/exhaust, but I personally think the 4EFE has alot more to show for itself! On another note, it would be wise to upgrade the suspension, and fit a rear anti roll bar, and stripping out the interior wouldn't do any harm either. Some good tyres help alot too.